REVISITING THE ROLE OF AGGREGATION IN THE SETTLING OF COHESIVE FLOCS IN THE MARINE ENVIRONMENT

Ashish J Mehta,William H Mcanally,Farzin Samsami,Andrew J Manning

doi:10.9753/icce.v36.sediment.17

Abstract

The settling velocity is the single-most important property governing the transport of cohesive flocs in the marine environment. In that regard, the instantaneously changing diameter, density and shear strength of flocs are the defining properties which distinguish floc transport from that of cohesionless particles. Thus, consideration of aggregation, which includes the dynamics of floc growth and breakup due to floc-floc collisions as well as flow-induced shearing of flocs, is a critical component of floc transport modeling.

Highlights

The settling velocity is the single-most important property governing the transport of cohesive flocs in the marine environment
Where wsh(G) is the peak settling velocity at the onset of hindered settling which occurs when φ > φh, n0 = 1/3 is a representative value of the exponent of φ/φh, and a0, λa and λb are sediment dependent constants independent of G
The present study is concerned with an effort to explain the physical underpinning of the five curves in Fig. 1 in terms of the application of the particle balance equation for the number concentration N of flocs of suspended cohesive sediment in the turbulent flow environment

Summary

Introduction

The settling velocity is the single-most important property governing the transport of cohesive flocs in the marine environment. The representation of floc settling velocity ws as a function solids volume fraction φ and the turbulent flow shear rate G Results in a settling velocity distribution dependent on the ranges of G and φ in the (local) natural environment.

Results

Conclusion